The project is concerned with the identification of genetic correlation's between several classes of behavior believed to be under partial control of the endogenous opioid system (EOP). One class would be the degree to which analysis of different strains are sensitive to the euphoric, as well as pain-modulating influences of marcotic drugs - morphine and heroin - and to the aversive properties of naloxone; the methods of conditioned place preference, hot-plate and tail-flick latencies will be employed for testing these variables. The second class is the degree to which animals of these strains are sensitive to cues such as sweet flavor or ethanol, the presence of which may induce overdrinking; daily intake of various fluids will be measured. The third class is the degree to which such animals are sensitive to prenatal stress influences on the differentiation of sexually dimorphic behavioral systems (e.g. mating or sweetness preference). Two strains of rats, LC2-Hi and LC2-Lo, which are selected for high and low rates of self-stimulation, and 10 recombinant inbred strains, derived from a cross of the LC2 strains, will be studied. The outcome of the research will be an animal model for the evaluation of the EOP system in intact organisms. Practical implications are - the assessment of sensitivity to the euphoric effects of narcotic drugs in individuals (e.g. high-risk drug abuse prediction) and possibly monitoring of the state of the EOP system in patients with putative anhedonic disturbances, using normal behavioral indices.